A high intensity procedure and one used mostly in an industrial set up, sandblasting refers to forcibly propelling a rush of abrasive material through a machine, under high pressure. There are several purposes for doing this. To roughen a smooth surface (or vice versa) or to maybe to get rid of substances contaminating the surface. Depending on the purpose, you will need to choose a sandblasting medium. The nature of your work, thus, determines what you need to use. The different types of media and their uses are mentioned below.
If the surface you are working on needs special finishing, then metallic mediums are a good option. For instance, you can opt for steel grit or shot. Using steel grit will make the surface etched, thus making it easier for the paint for adhere to that surface. On the other hand, for a smooth and polished finish, consider steel shot.
In case you haven't done this before and are a bit unsure about the whole thing, especially how well the surface will take the sandblasting media, a gentle medium will be a good option. One the most gentle and eco-friendly materials is walnut. Other such soft media are corncob and pumice.
A Tough Job
There are some surfaces which are tough to work upon. You need a harsher medium to tackle it. In this case, use a sand medium that is strong and hard. For example, silicon carbide is the hardest medium for sand blasting.
Apart from the options mentioned above, there are mediums which are used solely for cleaning machinery, electromechanical equipment, electrical installations, and other such surfaces, where the residue from standard sandblasting techniques could lead to a damage. Dry ice is used for these purposes.
Remember, you have to be particularly careful when you clean up. Small grains of aluminum oxide are present in the medium, which cannot be removed easily.
More About Sandblasting Media
Basically, there are three types of media―soft, medium, and high abrasives. They can also be classified as synthetic, mineral, and agricultural. Walnut shells and fruit kernels are classified as agricultural abrasives or as soft abrasives if they're mixed baking soda and plastic.
Crushed glass, beads, and ceramic beads are medium abrasives; whereas, silicon carbide and aluminum oxide are high or mineral mediums. Silica sand and garnet are mineral sandblasting media. Dry ice on the other hand is a synthetic medium.
Remember, exposure to some of the mediums mentioned above can prove to be a health risk. Always wear the right type of protective gear and then proceed with the job.